> For the complete documentation index, see [llms.txt](https://brightercommand.gitbook.io/paramore-brighter-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://brightercommand.gitbook.io/paramore-brighter-documentation/outbox-and-inbox/distributedlock/postgresdistributedlock.md).

# Postgres Distributed Lock

The Postgres locking provider implements Brighter's distributed lock using PostgreSQL advisory locks, so a single Outbox Sweeper and Archiver run when you scale out.

> **Reference** · Applies to **Brighter V10**

The Postgres locking provider implements Brighter's [distributed lock](/paramore-brighter-documentation/outbox-and-inbox/distributedlock.md) using PostgreSQL **advisory locks**, so a single [Outbox Sweeper](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport.md#implicit-clear) and Archiver run when you scale out. It pairs naturally with the [Postgres Outbox](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport/postgresoutbox.md).

## Postgres Distributed Lock Package

* **Paramore.Brighter.Locking.PostgresSql**

Advisory locks are a built-in PostgreSQL feature, so there is **no table to provision** — see [Provisioning](#postgres-distributed-lock-provisioning).

## Postgres Distributed Lock Configuration

Configure the provider with `PostgresLockingProvider`, passing a `PostgresLockingProviderOptions` that carries the connection string:

```csharp
using Paramore.Brighter.Locking.PostgresSql;

new PostgresLockingProvider(
    new PostgresLockingProviderOptions(
        connectionString: "Host=localhost;Database=orders;Username=app;Password=secret"));
```

| Option             | Type     | Default | Description                                     |
| ------------------ | -------- | ------- | ----------------------------------------------- |
| `connectionString` | `string` | `none`  | Opens the session that holds the advisory lock. |

That constructor parameter is the whole of the type: it surfaces as the get-only `ConnectionString`, and there is nothing else to set. In particular the provider does **not** take a [relational database configuration](/paramore-brighter-documentation/brighter-configuration/brighterbasicconfiguration/relationaldatabaseconfigurationreference.md), even though the Postgres Outbox beside it does.

## Postgres Distributed Lock Example

```csharp
using Microsoft.Extensions.DependencyInjection;
using Paramore.Brighter;
using Paramore.Brighter.Extensions.DependencyInjection;
using Paramore.Brighter.Locking.PostgresSql;
using Paramore.Brighter.Outbox.Hosting;
using Paramore.Brighter.PostgreSql;

const string connectionString = "Host=localhost;Database=orders;Username=app;Password=secret";

services.AddSingleton<IAmARelationalDatabaseConfiguration>(new RelationalDatabaseConfiguration(connectionString));

services
    .AddBrighter()
    .AddProducers(opt =>
    {
        opt.Outbox = outbox; // your Postgres Outbox
        opt.ConnectionProvider = typeof(PostgreSqlConnectionProvider);
        opt.TransactionProvider = typeof(PostgreSqlTransactionProvider);

        opt.DistributedLock = new PostgresLockingProvider(
            new PostgresLockingProviderOptions(connectionString));
    })
    .UseOutboxSweeper(opt => { opt.BatchSize = 10; });
```

## Postgres Distributed Lock Provisioning

None. PostgreSQL advisory locks are session-scoped locks that live in the server's memory, so the provider needs no table or schema. The lock is held for the lifetime of the database session and is released when that session closes — including if the holding instance crashes and its connection drops.

## Postgres Distributed Lock Notes

* Because the lock is tied to a session rather than a timed lease, there is no `LeaseValidity` to tune. Recovery after a crash happens as soon as the dropped connection is detected by the server.
* Point the provider at the same PostgreSQL instance as your Outbox so the Sweeper, Archiver, and lock all share infrastructure.

## Further Reading

* [Distributed Lock](/paramore-brighter-documentation/outbox-and-inbox/distributedlock.md) — concepts and the full provider list
* [Postgres Outbox](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport/postgresoutbox.md) — the matching Outbox
* [Outbox Support](/paramore-brighter-documentation/outbox-and-inbox/brighteroutboxsupport.md) — the Sweeper and Archiver


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